1. Field of the Invention
The present invention relates to an apparatus for controlling an elevator door in which the driving of a motor for opening and closing the elevator door is controlled by an inverter.
2. Description of the Related Art
FIG. 7 shows a mechanical structure of a general elevator door system. In FIG. 7, the elevator door system comprises a hanger case 1, a door controlling unit 2, a door driving motor 3 connected to the door controlling unit 2, and a driving unit 4 fixed to the upper side of the hanger case 1 and containing the motor 3. A door 6 provided at the entrance of a cage is connected to the driving unit 4 through a four-throw driving link 5. On the door 6 are provided an engaging unit 7 which is engaged with the unit (not shown) provided on a door at a riding place within a door zone so as to link the door 6 to the door at each riding place, and a door hanger 11 which is moved by hanger rollers 9 and up thrust rollers 10 for guiding the door 6 to be opened and closed on a rail 8. The hanger case 1 is provided with a door stopper 12 at the opening end and a door stopper 13 on a closing end, both of which are made of an elastic material, as well as an OLT sensor 14 indicating an open state of the door 6 and a CLT sensor 15 indicating a closed state of the door 6. A door stopper 16 which strikes the door stoppers 12 and 13 and a fitting 17 for actuating the OLT sensor 14 and the CLT sensor 15 are also fixed to the door hanger 11.
FIG. 8 shows the circuit arrangement of the conventional door controlling unit 2 for controlling the above-described elevator door system.
For example, a three-phase alternating current of 200 V or 220 V, which is input from a power source, is rectified by a diode bridge 20 and smoothed by a smoothing capacitor 21 to generate a dc voltage. The dc voltage is controlled to a sine-wave motor current by an inverter 22 comprising switching elements such as transistors, FETs or the like. During this control, the switching elements of the inverter 22 are subjected to pulse width modulation by the PWM pulse generated from a PWM section 27. In this way, the speed and torque of the door driving motor 3 are controlled.
The speed of the door driving motor 3 is detected by an encoder 23 provided on the motor shaft. The speed .omega..sub.r.sup.* detected by the encoder 23 is subtracted from the speed command .omega..sub.r generated from a speed command generator 30 in a microcomputer 24 at a subtraction section 31 to determine a speed deviation .DELTA..omega..sub.r. When the speed deviation .DELTA..omega..sub.r is input to a speed amplifier 32, the amplifier 32 calculates torque necessary for the door driving motor 3 in accordance with the speed command .omega..sub.r and inputs to a slip calculating section 34 a torque command, i.e., a current iq corresponding to the torque and a current command id corresponding to excitation, which is generally a constant value within a constant torque region. The slip calculating section 34 generates a slip frequency .omega..sub.s. The slip frequency .omega..sub.s is added to the speed .omega..sub.r.sup.* detected by the encoder 23 at a first addition section 36 and then input to a phase counter 37 serving as an integrator. In the phase counter 37, the rotational angle of the driving motor 3 is calculated by the equation, .theta..sub.r =.intg.(.omega..sub.r.sup.* .+-..omega..sub.s) dt.
The phase angle .theta.i, which is calculated from the current iq corresponding to the torque and the current command id corresponding to excitation by a phase angle calculating section 35, is added to the rotational angle .theta..sub.r of the magnetic field at a second addition section 38 to determine an actual current phase angle .theta.=.theta..sub.r +.theta.i. From the phase angle .theta. and the current amplitude .vertline.I.vertline. generated from a current amplitude calculating section 33, a current command generating section 39 generates a U-phase current command I.sub.u =.vertline.I.vertline..multidot.sin .theta. and a v-phase current command I.sub.v =.vertline.I.vertline..multidot.sin (.theta.+2/3 .pi.). From the current commands and the actual motor currents I.sub.u.sup.*, I.sub.v.sup.*, which are respectively detected by dc CTs 25, deviations .DELTA.I.sub.u, .DELTA.I.sub.v and .DELTA.I.sub.w =-.DELTA.I.sub.u -.DELTA.I.sub.v are determined by a DC amplifier 26. A three-phase PWM voltage command corresponding to the three deviation values is generated from the PWM section 27. The pulse train is supplied to the inverter 22 so as to actuate the switching elements thereof. This permits the current, voltage and frequency of the door driving motor 3 to be respectively controlled to predetermined values. The above-described series of operations control the rotational speed and the torque of the door driving motor 3.
For example, as shown in FIG. 9, the door 6 is controlled by pressing the door stopper 16 against the stoppers 12 and 13, both of which are made of an elastic material, with predetermined torque at the opening and closing ends of the door 6.
The above conventional elevator door controlling unit has the problem that the door 6 is pushed back by the reaction force of the stopper 13 at the moment the door stopper 16 collides with the stopper 13 and produces vibration setting of the actual speed .omega..sub.r.sup.* even if the speed command .omega..sub.r is constant, as shown in FIG. 9.
The elevator door controlling unit also has the problems that, when the closed door is forced open by tampering or the like, the actual speed .omega..sub.r.sup.* cannot be easily correctly detected because it is a low value, and the reaction force to prevent the door from being forced open cannot be easily generated, and that heat is generated from the motor if the current at the time the door stopper 16 is pressed against the stopper 13 is increased.